The present invention relates to foamed erasers based on polyvinylchloride (PVC) and/or PVC/PVA (polyvinylacetate) mixed polymerizate plastisols or plasticized flowable mixtures, and more particularly to the process for the production of that type of foamed erasers.
Previously known foamed rubber erasers evidence extremely coarse porous and non-uniform structures. As a rule, they are produced in a manner such that the initial charge medium, which is suitable for the respective basic substance desired, deteriorates under elevated temperature with gas being given .
Due to this exothermic, irreversible, deterioration process, the erasing compound produced possesses individual hollow spaces, which cannot be regulated, either in terms of their size or their uniform distribution within the entire compound, in a controllable manner.
Moreover, rubber erasers of this type cannot be continuously produced. In general, previously employed processes involve foaming the latex mixtures, PVC-plastisol or similar flowable materials in continuous foaming agitators with the addition of air or other gas infeed with mixing.